Methods and devices for performing proximity discovery

ABSTRACT

A method for use in a first user equipment (UE) includes receiving, from a base station, control information and a resource assignment for uplink transmission; and transmitting, based on the control information, a discovery signal on the assigned resource for uplink transmission, the discovery signal including a first temporary UE identifier (ID) assigned to the first UE, wherein the first temporary UE ID is used to identify the first UE for device-to-device communication.

FIELD

This application generally relates to methods and devices for performingproximity discovery for device-to-device communication.

BACKGROUND

In cellular networks such as Long Term Evolution (LTE) and LTE-Advancedcommunication networks, a user equipment (UE) may communicate with otherUEs via a base station and an evolved packet core (EPC) network. Forexample, a UE may send data packets to its serving base station on anuplink. The serving base station may forward the data packets to the EPCnetwork, and the EPC network may forward the data packets to anotherbase station or to the same base station that is serving another UE.Data transfer between the UEs is routed through the base station and theEPC network. The communication between the UEs is controlled by thepolicies set by the operator administering the network.

The UEs may communicate directly with each other using another radioaccess technology (RAT), such as a wireless local area network (WLAN) orBluetooth, when the UEs are located in close proximity and have accessto the other RAT. However, this multi-RAT communication generallyrequires the availability of the other RAT and the capability of the UEsto operate in the other RAT. Moreover, handover from cellular technologyto the other RAT may result in service interruption and dropped calls.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof this specification, and together with the description, illustrate andserve to explain various examples.

FIG. 1 illustrates a cellular wireless communication system, accordingto an example approach.

FIG. 2 illustrates a block diagram of an access node device, accordingto an example approach.

FIG. 3 illustrates a block diagram of user equipment (UE), according toan example approach.

FIGS. 4 and 5 are flow diagrams of methods for performing proximitydiscovery, according to example approaches.

FIG. 6 is a diagram illustrating assignment of a physical downlinkshared channel (PDSCH) via a physical downlink control channel (PDCCH),according to an example approach.

FIGS. 7 a and 7 b show formats of the PUSCH, according to exampleapproaches.

FIG. 8 is a diagram showing multiplexing UEs, according to an exampleapproach.

FIGS. 9-11 are diagrams illustrating methods for a UE to transmit adiscovery signal on a physical uplink control channel (PUCCH), accordingto example approaches.

DETAILED DESCRIPTION

The present disclosure is directed to devices and methods for performingproximity discovery for inter-device communication in cellular wirelesscommunication systems. When a first user equipment (UE) in a cellularwireless network is located in close proximity with a second UE, itwould be advantageous for the first UE to discover the second UE, orvice versa, such that they can communicate via a direct inter-devicecommunication link between them, instead of transferring the data viathe network. By providing a direct inter-device communication linkbetween UEs, the UEs can receive proximity services (ProSe), and overallspectral efficiency may also be improved. Moreover, the direct linkbetween the UEs generally requires lower transmit power at the UEcompared to transmitting to a base station, thereby resulting in batterysavings at the UEs. Additionally, it may be advantageous to enablecommunications over the inter-device communication link using the samecellular radio access technology (RAT).

Reference will now be made in detail to example approaches, which areillustrated in the accompanying drawings. The following descriptionrefers to the accompanying drawings in which the same numbers indifferent drawings represent the same or similar elements unlessotherwise represented. The implementations set forth in the followingdescription of example approaches do not represent all implementations.Instead, they are merely examples of devices and methods consistent withaspects related to the appended claims.

FIG. 1 illustrates an example cellular wireless communication system 100in which methods and devices consistent with this disclosure may beimplemented. The system 100 may include one or more base stations, andoperate according to a wireless communication standard, such as a LongTerm Evolution (LTE) standard. In the example LTE system 100, the basestations are shown as evolved Node Bs (eNBs), e.g., eNB 112 a and eNB112 b, although base stations can operate in any wireless communicationssystem, including for example, a macro cell, a femto cell, a relay cell,and a pico cell. Base stations are nodes that can relay signals for userequipment (UE) or for other base stations. The base stations are alsoreferred to as access node devices. The example LTE telecommunicationsenvironment of FIG. 1 includes a radio access network such as an EvolvedUniversal Terrestrial Radio Access Network (EUTRAN) 110 including theeNB 112 a and the eNB 112 b, a core network (CN) such as an evolvedpacket core (EPC) 120, and an external network such as an InternetProtocol (IP) network 130. Further, as shown, one or more UEs, such as aUE 102 a and a UE 102 b, operate within the example LTE system 100. Insome implementations, 2G/3G systems 140, e.g., Global System for MobileCommunications (GSM), Interim Standard 95 (IS-95), Universal MobileTelecommunications System (UMTS), or Code Division Multiple Access 2000(CDMA2000) may also be integrated into the system 100.

In example approaches, the EUTRAN 110 may include one or more eNBs, suchas the eNB 112 a and the eNB 112 b. A cell 114 a is a coverage area ofthe eNB 112 a, and a cell 114 b is a coverage area of the eNB 112 b. Oneor more UEs, e.g., the UEs 102 a and 102 b, can operate in the cell 114a and be served by eNB 112 a. The eNBs 112 a and 112 b can communicatedirectly to the UEs 102 a and 102 b. In some implementations, the eNB112 a or 112 b may be in a one-to-many relationship with UEs, e.g., theeNB 112 a can serve the UE 102 a and the UE 102 b within its coveragearea, i.e., the cell 114 a, but each of the UE 102 a and the UE 102 bmay be connected to one serving eNB at a time. In some implementations,the eNBs 112 a and 112 b may be in a many-to-many relationship with UEs,e.g., the UE 102 a and the UE 102 b may be connected to the eNB 112 aand the eNB 112 b. The eNB 112 a may be connected to the eNB 112 b suchthat handover may be conducted if one or both of the UEs 102 a and 102 btravels, e.g., from the cell 114 a to the cell 114 b.

The UEs 102 a and 102 b may be any wireless electronic device used by anend-user. The UEs 102 a and 102 b may transmit voice, data, video,multimedia, text, web content and/or any other user/client-specificcontent. The transmission of some content, e.g., video and web content,may require high channel throughput to satisfy the end-user demand. Insome instances, however, a channel between the UE 102 a or 102 b and theeNB 112 a or 112 b may be contaminated by, e.g., multipath fading whichmay be due to the multiple signal paths arising from many reflections inthe wireless environment. Accordingly, transmission of the UEs 102 a and102 b may adapt to the wireless environment. In short, the UEs 102 a and102 b may generate requests, send responses or otherwise communicate indifferent means with the EPC 120 and/or the IP network 130 through oneor more eNBs 112 a and 112 b.

In some implementations, the UEs 102 a and 102 b may communicate over aninter-device communication link 104 when they are located in closeproximity to one another, without routing communication data through theeNB 112 a or 112 b. The boundary of the distance of the inter-devicecommunication link may be limited by the transmission power of the UEs102 a and 102 b. In one example, close proximity could be a few meters.In another example, close proximity could be tens of meters. It is alsopossible that in certain circumstances, the close proximity may meanlarger distance such as hundreds of meters or more. For example, the UEs102 a and 102 b may communicate directly over the inter-devicecommunication link 104, instead of communicating with each other throughtheir links 106 and 108 with the eNB 112 a, respectively. Theinter-device communication link may also be referred to as adevice-to-device (D2D) communication link. The UEs 102 a and 102 b maysimultaneously maintain an active communication link with the eNB 112 asuch that the UEs 102 a and 102 b may still receive messages from theeNB 112 a or other UEs, when communicating with each other over thedirect inter-device link 104.

Examples of UEs include, but are not limited to, a mobile phone, a smartphone, a telephone, a television, a remote controller, a set-top box, acomputer monitor, a computer (including a tablet computer, a desktopcomputer, a handheld or laptop computer, a netbook computer), a personaldigital assistant (PDA), a microwave, a refrigerator, a stereo system, aDVD player or recorder, a CD player or recorder, an MP3 player, a radio,a camcorder, a camera, a digital camera, a portable memory chip, awasher, a dryer, a washer/dryer, a copier, a facsimile machine, ascanner, a multi-functional peripheral device, a wristwatch, a clock, agame device, etc. The UE 102 a or 102 b may include a device and aremovable memory module, such as a Universal Integrated Circuit Card(UICC) that includes a Subscriber Identity Module (SIM) application, aUniversal Subscriber Identity Module (USIM) application, or a RemovableUser Identity Module (R-UIM) application. Alternatively, the UE 102 a or102 b may include the device without such a module. The term “UE” canalso refer to any hardware or software component that can terminate acommunication session for a user. In addition, the terms “userequipment,” “UE,” “user equipment device,” “user agent,” “UA,” “userdevice,” and “mobile device” are used synonymously herein.

A radio access network (RAN) is part of a mobile telecommunicationsystem which implements a radio access technology, such as UniversalMobile Telecommunications System (UMTS), CDMA2000 and 3rd GenerationPartnership Project (3GPP) LTE. For example, the RAN included in theexample LTE system 100 is the EUTRAN 110. The EUTRAN 110 can be locatedbetween the UEs 102 a, 102 b and the EPC 120. The EUTRAN 110 includes atleast one eNB 112 a or 112 b. Each eNB can be a radio base station thatmay control all, or at least some, radio related functions in a fixedpart of the system. One or more of the eNBs 112 a and 112 b can provideradio interface within their coverage area or a cell for the UEs 102 a,102 b to communicate. The eNBs 112 a and 112 b may be distributedthroughout the cellular network to provide a wide area of coverage. TheeNBs 112 a and 112 b may directly communicate with one or more of theUEs 102 a and 102 b, other eNBs, and the EPC 120.

The eNBs 112 a and 112 b may be an end point of the radio protocolstowards the UEs 102 a, 102 b and may relay signals between the radioconnection and the connectivity towards the EPC 120. The communicationinterface between the eNB 112 a or 112 b and the EPC 120 is oftenreferred to as an S1 interface. In certain implementations, the EPC 120is a central component of the core network (CN). The CN can be abackbone network, which may be a central part of the telecommunicationssystem. The EPC 120 can include a mobility management entity (MME), aserving gateway (S-GW), and a packet data network gateway (PGW). The MMEmay be the main control element in the EPC 120 responsible for thefunctionalities comprising the control plane functions related tosubscriber and session management. The SGW can serve as a local mobilityanchor, such that data packets are routed through this point for intraEUTRAN 110 mobility and mobility with other legacy 2G/3G systems 140.The S-GW functions may include user plane tunnel management andswitching. The PGW may provide connectivity to the services domaincomprising external networks 130, such as the IP networks. The UEs 102 aand 102 b, the EUTRAN 110, and the EPC 120 are sometimes referred to asthe evolved packet system (EPS). It is to be understood that thearchitectural evolvement of the example LTE system 100 is focused on theEPS. The functional evolution may include both the EPS and the externalnetwork 130.

Though described in terms of FIG. 1, the present disclosure is notlimited to such an environment. In general, cellular telecommunicationsystems may be described as cellular networks made up of a number ofradio cells, or cells that are each served by a base station or otherfixed transceiver. The cells are used to cover different locations inorder to provide radio coverage over an area. Example cellulartelecommunication systems include Global System for Mobile Communication(GSM) protocols, Universal Mobile Telecommunications System (UMTS), 3GPPLong Term Evolution (LTE), and others. In addition to cellulartelecommunication systems, wireless broadband communication systems mayalso be suitable for the various implementations described in thepresent disclosure. Example wireless broadband communication systemsinclude IEEE 802.11 WLAN, IEEE 802.16 WiMAX network, etc.

FIG. 2 illustrates a block diagram of an access node device 200,according to an example approach. For example, the access node device200 may be a base station, such as the eNB 112 a or 112 b (FIG. 1).Referring to FIG. 2, the access node device 200 includes a processingmodule 202, a wired communication subsystem 204, and a wirelesscommunication subsystem 206. The processing module 202 can include oneor more processing components (alternatively referred to as “processors”or “central processing units” (CPUs)) operable to execute instructionsassociated with managing (inter-device-driver) IDC interference. Theprocessing module 202 can also include other auxiliary components, suchas random access memory (RAM), read only memory (ROM), secondary storage(for example, a hard disk drive or flash memory). Additionally, theprocessing module 202 can execute certain instructions and commands toprovide wireless or wired communication, using the wired communicationsubsystem 204 or the wireless communication subsystem 206. One skilledin the art will readily appreciate that various other components canalso be included in the example access node device 200 without departingfrom the principles of the present disclosure.

FIG. 3 illustrates a block diagram of a UE 300, according to an exampleapproach. Referring to FIG. 3, the UE 300 includes a processing unit302, a tangible, non-transitory computer readable storage medium 304(for example, ROM or flash memory), a wireless communication subsystem306, a user interface 308, and an I/O interface 310.

The processing unit 302 may include components and perform functionalitysimilar to the processing module 202 described with regard to FIG. 2.The wireless communication subsystem 306 may be configured to providewireless communications for data information or control informationprovided by the processing unit 302. The wireless communicationsubsystem 306 can include, for example, one or more antennas, areceiver, a transmitter, a local oscillator, a mixer, and a digitalsignal processing (DSP) unit. In some implementations, the wirelesscommunication subsystem 306 may receive or transmit information over adirect inter-device communication link. In some implementations, thewireless communication subsystem 306 can support MIMO transmissions.

The user interface 308 can include, for example, one or more of a screenor touch screen (for example, a liquid crystal display (LCD), a lightemitting display (LED), an organic light emitting display (OLED), amicroelectromechanical system (MEMS) display, a keyboard or keypad, atracking device (e.g., trackball, trackpad), a speaker, and amicrophone).

The I/O interface 310 can include, for example, a universal serial bus(USB) interface. One skilled in the art will readily appreciate thatvarious other components can also be included in the example UE device300.

For UEs to perform device-to-device (D2D) communication over a directinter-device communication link, an inter-device communication link isenabled between the UEs. The direct inter-device communication linkallows data exchange between the UEs, without routing through a basestation and a core network.

FIG. 4 is a flow diagram of a method 400 for performing proximitydiscovery, according to an example approach. In the illustratedapproach, a plurality of UEs, including a first UE and a second UE, arein a coverage area of a base station in a wireless network. For example,the first UE and the second UE may be the UEs 102 a and 102 b (FIG. 1),respectively, and the base station may be the eNB 112 a (FIG. 1).

Referring to FIG. 4, the first UE sends the base station an indicationmessage indicating its capability of performing D2D communication (402).For example, the first UE may send the indication message whenperforming network entry. Also for example, the first UE may send theindication message in response to a request from the base station. Asanother example, the first UE may send the indication message when thefirst UE attempts to initiate D2D communications. In one exampleapproach, the first UE may modify an existing radio resource control(RRC) uplink (UL) message with a new information element (IE) togenerate the indication message. In another example approach, the firstUE may generate the indication message by generating a new RRC ULmessage, e.g., a UE capability indication message. Similarly, the secondUE also sends the base station an indication message indicating itscapability of performing D2D communication (402). One or more additionalUEs in the coverage area (not shown) may also send a similar indicationto the base station.

The base station receives the indication messages from the UEs and, inresponse, assigns a temporary D2D UE identifier (ID) to each of the UEs(404). A temporary D2D UE ID may be used to deliver resource assignmentto a UE involved in D2D communications, and also used to identify the UEinvolved in D2D communications. A temporary D2D UE ID may be releasedwhen the UE leaves D2D communications, e.g., when the UE physicallyleaves the coverage area of the base station, or when the UE indicatesto the base station its desire to leave. As a result, each of the UEsreceives its assigned temporary D2D UE ID from the base station.

In example approaches, the first UE wants to initiate proximitydiscovery. Accordingly, the first UE, referred to hereafter as thetarget UE, sends a discovery signal transmission request to the basestation (406). For example, the target UE may send the discovery signaltransmission request via a modified existing RRC message or a new RRCmessage. Also for example, the target UE may send the discovery signaltransmission request via a new media access control (MAC) controlelement (CE) or a reserved field in an existing MAC CE.

After receiving the discovery signal transmission request, the basestation may grant the request by transmitting on, e.g., a physicaldownlink control channel (PDCCH), control information and a resourceassignment for uplink transmission to the target UE (408). For example,the resource assignment for uplink transmission may assign a physicaluplink shared channel (PUSCH) or a physical uplink control channel(PUCCH). The base station also transmits to the second UE, referred tohereafter as the anchor UE, an announcement message on the PDCCH tonotify the anchor UE of the resource assignment for uplink transmission(410). In some approaches, the base station may receive multiplediscovery signal transmission requests from multiple target UEs.Accordingly, the base station may grant the multiple requests on thePDCCH. Similarly, the base station may send the announcement message tomultiple anchor UEs. e.g., those that did not send a discovery signaltransmission request. In some approaches, a target UE that sends adiscovery signal may also be an anchor UE that receives a discoverysignal from another UE.

In example approaches, the base station may select resources for uplinktransmission, e.g., based on channel state information (CSI) feedbackfrom the UEs. Alternatively and/or additionally, the base station maydedicate resources for uplink transmission. The base station may alsoselect resources for uplink transmission in a round robin manner orrandomly to enhance discovery probability at a given time. For example,round-robin (RR) is a scheduling method in which time slices areassigned to each transmission process in circular order, such that thebase station may handle all processes without priority.

In example approaches, the base station may include error detection in amessage. For example, the base station may generate a cyclic redundancycheck (CRC) code for a message including the resource assignment foruplink transmission, which can provide error detection for decoding themessage, so that a UE, e.g., the first UE, can determine whether it hascorrectly received the message on the PDCCH. Furthermore, the basestation may scramble the generated CRC code with an identifier of the UEfor proximity discovery, e.g., a radio network temporary identifier(RNTI) assigned to the UE, such that the UE can identify informationintended for it on the PDCCH. Alternatively, the base station mayinclude the identifier of the UE in a payload of the PDCCH.

In one example approach, the RNTI of the UE may have a hexadecimal valuein a predetermined range from FFF4 to FFFC. In one example approach, theRNTI of the UE may have a predetermined value 0000. In one exampleapproach, the RNTI of the UE may have a hexadecimal value in apredetermined range from 0001 to FFF3.

In example approaches, the PDCCH may carry uplink resource assignmentand control information for a UE or a group of UEs with the RNTI. ThePDCCH is generally transmitted on an aggregation of one or severalconsecutive control channel elements (CCEs), where a control channelelement may correspond to a predetermined number of resource elementgroups, e.g., 9 resource element groups.

In example approaches, control information transmitted on the PDCCH mayinclude a flag to differentiate between Format 0 and Format 1A of thePDCCH provided in the LTE standard, a flag to differentiate betweenFormat 0 and a current format, resource assignments for uplinktransmission and downlink transmission, and a frequency hopping flagindicating if a frequency hopping is applied. Control informationtransmitted on the PDCCH may also include a number of target UEsrequesting proximity discovery, their assigned temporary D2D UE IDs,information regarding discovery signals to be transmitted by the targetUEs including, e.g., patterns, locations, and modulation and codingschemes (MCSs) for the discovery signals, and power control commands forthe assigned PUSCH. Control information transmitted on the PDCCH mayadditionally include a request for an acknowledgement ornegative-acknowledgement (ACK/NACK) of proximity discovery, and apre-configured bitmap representing a hopping pattern if a frequencyhopping is applied.

The target UE then decodes the PDCCH to receive the resource assignmentfor uplink transmission and the control information (412), and theanchor UE decodes the PDCCH to obtain information regarding the resourceassignment for uplink transmission (414).

The target UE may then transmit, based on the received controlinformation, a discovery signal including the temporary D2D UE ID of thetarget UE, on the assigned resource for uplink transmission, such as onthe PUSCH or on the PUCCH (416), or on the PDSCH. In one exampleapproach, the target UE may broadcast the discovery signal. Because theanchor UE obtains the information regarding the resource assignment foruplink transmission, the anchor UE detects the discovery signalincluding the temporary D2D UE ID of the target UE and further transmitsa reporting message to the base station reporting the temporary D2D UEID being detected (418). For example, the anchor UE may transmit thereporting message to the base station on the PUCCH or on the PUSCH.Similarly, in some approaches, other target UEs in the coverage area ofthe base station may transmit discovery signals on their assignedresource for uplink transmission, and other anchor UEs in the coveragearea may report detection of temporary D2D UE IDs to the base station.The anchor UEs may consolidate the detection of multiple target UEs inthe same reporting, e.g., on the PUCCH or on the PUSCH.

Still referring to FIG. 4, after receiving the reporting message fromthe anchor UE, the base station performs an authentication on arelationship between the anchor UE and the target UE (420). Uponauthentication, the base station transmits the temporary D2D UE ID ofthe anchor UE to the target UE (422). The target UE and the anchor UEmay then perform D2D communication using close proximity RAT, orcontinue proximity discovery (424).

FIG. 5 is a flow diagram of a method 500 for performing proximitydiscovery, according to an example approach. In the illustratedapproach, a plurality of UEs including a first UE and a second UE are ina coverage area of a base station in a wireless network. For example,the first UE and the second UE may be the UEs 102 a and 102 b (FIG. 1),respectively, and the base station may be the eNB 112 a (FIG. 1).

Referring to FIG. 5, the first UE sends the base station an indicationmessage indicating its capability of performing D2D communication (502).For example, the first UE may send the indication message whenperforming network entry. Also for example, the first UE may send theindication message in response to a request from the base station. Inone approach, the first UE may modify an existing radio resource control(RRC) uplink (UL) message with a new information element (IE) togenerate the indication message. In another approach, the first UE maygenerate the indication message by generating a new RRC UL message,e.g., a UE capability indication message. Similarly, the second UE andany other UEs in the coverage area each also send the base station anindication message indicating its capability of performing D2Dcommunication (502).

The base station receives the indication messages from the UEs and, inresponse, assigns a temporary D2D UE identifier (ID) to each of the UEs(504). Thus, each of the UEs receives its assigned temporary D2D UE IDfrom the base station.

In example approaches, the first UE initiates proximity discovery.Accordingly, the first UE, referred to hereafter as the target UE, sendsa discovery signal transmission request to the base station (506). Forexample, the target UE may send the discovery signal transmissionrequest via a modified existing RRC message or a new RRC message. Alsofor example, the target UE may send the discovery signal transmissionrequest via a new media access control (MAC) control element (CE) or areserved field in an existing MAC CE.

After receiving the discovery signal transmission request, the basestation grants the request by transmitting on a PDCCH a resourceassignment for a physical downlink shared channel (PDSCH), and furthertransmitting on the PDSCH control information and resource assignmentfor uplink transmission to the target UE (508). For example, the basestation may receive multiple discovery signal transmission requests frommultiple target UEs, and the PDCCH may not provide sufficient timeand/or frequency resources to transmit control information and resourceassignments for uplink transmission. Accordingly, the base stationtransmits the control information and the resource assignments foruplink transmission on the PDSCH via the PDCCH. Also for example, theresource assignment for uplink transmission may assign a PUSCH or aPUCCH.

FIG. 6 is a diagram illustrating an example approach wherein the basestation assigns a PDSCH via a PDCCH. Referring to FIG. 6, the basestation assigns a part 602 of the PDCCH to transmit the resourceassignment for a part 604 of the PDSCH, and further assigns the part 604of the PDSCH to transmit the control information and the resourceassignment for uplink transmission. When the UE decodes the part 602 ofthe PDCCH, the UE knows where on the PDSCH to receive the controlinformation and the resource assignment for uplink transmission, i.e.,the part 604 of the PDCCH.

Referring back to FIG. 5, the base station also transmits to the secondUE, referred to hereafter as the anchor UE, an announcement message onthe PDCCH to notify the anchor UE of the resource assignment for uplinktransmission (510). In addition, the base station may use a CRC code anda RNTI for transmission on the PDCCH, similar to the above descriptionin connection with FIG. 4.

In some approaches, control information transmitted on the PDSCH mayinclude uplink resource assignments for discovery signals at subframe n;a time offset from a current subframe k, where 1<k<P and P is aconfigurable parameter that can be defined by the network; and a numberof target UEs that transmit discovery signals at subframe n+k. Controlinformation transmitted on the PDSCH may also include a duration fortransmitting discovery signals; temporary D2D UE IDs of the target UEs;and a bitmap representing a hopping pattern if resource hopping is usedin the duration for transmitting discovery signals. Control informationtransmitted on the PDSCH may further include information regardingdiscovery signals to be transmitted by the target UEs including, e.g.,patterns, locations, and modulation and coding schemes (MCSs), DM-RSlocations, cyclic shift information, a number of bits of each temporaryD2D UE ID, a number of assigned resource blocks (RBs), etc. Controlinformation transmitted on the PDSCH may additionally include timingadvance of the target UEs that transmit proximity discovery signals,which may be used for distance estimation between UEs, and the temporaryD2D UE ID of the anchor UE if groupcast is supported by the network.

As a result, the target UE may decode the PDCCH and further decode thePDSCH to receive the control information and the resource assignment foruplink transmission (512), and the anchor UE may decode the PDCCH andfurther decode the PDSCH to obtain information regarding the resourceassignment included in the announcement message (514).

The target UE may then transmit, based on the received controlinformation, a discovery signal, including the temporary D2D UE ID ofthe target UE, on the assigned resource for uplink transmission, such ason the PUSCH or on the PUCCH (516). Since the anchor UE obtains theinformation regarding the resource assignment for uplink transmission,the anchor UE detects the discovery signal including the temporary D2DUE ID of the target UE, and further transmits a reporting message to thebase station reporting the temporary D2D UE ID being detected (518).Similarly, other target UEs in the coverage area of the base station maytransmit discovery signals on their assigned resource for uplinktransmission, and other anchor UEs in the coverage area may reportdetection of temporary D2D UE IDs to the base station. The anchor UEsmay consolidate the detection of multiple target UEs in the samereporting.

Still referring to FIG. 5, after receiving the reporting message fromthe anchor UE, the base station performs an authentication on arelationship between the anchor UE and the target UE (520). Uponauthentication, the base station transmits the temporary D2D UE ID ofthe anchor UE to the target UE (522). The target UE and the anchor UEmay then perform D2D communication using close proximity RAT, orcontinue proximity discovery (524).

In example approaches, based on the resource assignment for uplinktransmission received from the base station, the target UE may transmitthe discovery signal on the PUSCH. For example, the target UE encodesits temporary D2D UE ID using a tail-biting convolutional code or aturbo code to generate the discovery signal, and transmits the generateddiscovery signal on the PUSCH.

FIGS. 7 a and 7 b show formats 702 and 704, respectively, of the PUSCH,according to example approaches. For example, each of the formats 702and 704 may include multiple symbols, such as 14 single carrierfrequency division multiple access (SC-FDMA) symbols, each representedby one column in the format. In the illustrated approach in FIG. 7 a,the PUSCH format 702 may consist of, e.g., 144 available resourceelements corresponding to 12 subcarriers (not shown) and 12non-reference symbols. Accordingly, for example, 144 bits of temporaryD2D UE ID information, including CRC bits, may be transmitted, if aquadrature phase shift keying (QPSK) modulation and a rate-½ tail-bitingconvolutional code are used. In the illustrated approach in FIG. 7 b,the PUSCH format 704 may include the first and last symbols used forguard interval. In this case, for example, 120 resource elements,corresponding to 12 subcarriers (not shown) and 10 non-referencesymbols, may be used to carry temporary D2D UE ID information includingCRC bits. Further, the guard interval may be used as auxiliary referencesignals to enhance quality of channel estimates. Thus, in theillustrated approach of FIG. 7 b, reference signals in the 4^(th) and11^(th) symbols may be repeated on the first and last symbols for theauxiliary reference signals, respectively, to thereby mitigateinterference from other UEs. In some approaches, additional referencesignals may be included in the symbols. For example, the 3^(rd) and10^(th) symbols may further be assigned to include reference signals.

In example approaches, a number of resource blocks on the PUSCH may beconfigured based on a bit length of temporary D2D UE IDs transmitted onthe PUSCH. Cyclic shift for multiplexing UEs and channel coding may alsobe applied to map a temporary D2D UE ID into multiple resource blocks.Hence, cyclic shift and orthogonal codes may be applied to discoverysignals to provide the multiplexing capability.

In example approaches, time-division multiplexing (TDM),frequency-division multiplexing (FDM) and/or code-division multiplexing(CDM) may be implemented to provide multi-user multiplexing gains fordiscovery signals transmitted on the allocated PUSCH resource. Inanother approach, multiple resource blocks on the PUSCH are assigned fordiscovery signal transmission, and a different combination of UEs maytransmit discovery signals in a resource block, which are also referredto as multiplexing UEs.

FIG. 8 is a diagram showing multiplexing UEs, according to an exampleapproach. In the illustrated approach, it is assumed that UE1, UE2, . .. , and UE8 transmit their respective discovery signals on the PUSCH.Further, a first resource block group (RBG) 802 including resourceblocks RB_(1,0), RB_(2,0), RB_(3,0), and RB_(4,0) correspond to a firsttime slot, Slot0, and a second RBG 804 including resource blocksRB_(1,1), RB_(2,1), RB_(3,1), and RB_(4,1) correspond to a second timeslot, Slot1. As shown in FIG. 8, a different combination of UEstransmits discovery signals in each resource block in the RBG 802 or804.

In example approaches, based on the resource assignment for uplinktransmission received from the base station, one or more target UEs maytransmit the discovery signal on the PUCCH. For example, multiple UEsmay transmit their respective discovery signals on the PUCCHsimultaneously. In some approaches, some UEs may transmit theirrespective discovery signals over the allocated PUSCH resource, whilesome UEs may transmit their respective discovery signals over theallocated PUCCH resource.

FIG. 9 is a diagram illustrating a method 900 for a target UE totransmit a discovery signal on the PUCCH, according to an exampleapproach. Referring to FIG. 9, the target UE may use a channel encoderto encode its assigned temporary D2D UE ID, which has a length of, e.g.,10 bits, with a Reed-Muller code, such as a (32, k) Reed-Muller code, togenerate 32 coded bits, and punctures the 32 bits to 24 bits (902),where k is the bit length of the temporary D2D UE ID. The target UE maythen modulate the 24 bits with the QPSK modulation (904). The target UEmay further multiply the QPSK output with each orthogonal code, e.g.,w₀, w₁, . . . , and w₄, in a set of orthogonal codes (906), apply cyclicshift (CS) codes CS0, CS2, CS3, CS4, and CS6 (908), apply discreteFourier transforms (DFTs) (910), and apply inverse fast Fouriertransforms (IFFTs) (912), to generate a plurality of symbols, e.g.,Sym0, Sym1, . . . , and Sym4, including information regarding thetemporary D2D UE ID. The target UE may additionally generate symbolsincluding demodulation reference signals (DM-RS) by applying CS codesCS1 and CS5 (914) and IFFTs (916) to a Zadoff-Chu (ZC) base sequence.Accordingly, the target UE may transmit the discovery signal, includingthe symbols Sym0, Sym1, . . . , and Sym4 and the reference symbols DM-RSin a resource block on the PUCCH. In example approaches, when the lengthof the temporary D2D UE ID is larger than 10 bits, the target UE maytransmit the temporary D2D UE ID on two or more resource blocks. In someapproaches, the target UE may transmit a discovery signal using a subsetof the elements in FIG. 9, e.g., based on the number of symbols includedin a resource block.

FIG. 10 is a diagram illustrating a method 1000 for a target UE totransmit a discovery signal on the PUCCH, according to an exampleapproach. Referring to FIG. 10, the target UE may use a channel encoderto encode its assigned temporary D2D UE ID, which has a length of, e.g.,10 bits, with a Reed-Muller code, such as a rate ½ punctured (20, k)Reed-Muller code, to generate 20 coded bits (1002). The target UE maythen modulate the first 10 bits of the 20 bits with the QPSK modulation(1004) followed by a serial-to-parallel (S/P) conversion (1006). For theoutput of the S/P conversion, the target UE may further apply CS codesCS0, CS2, CS3, CS4, and CS6 (1008), and apply inverse discrete Fouriertransforms (IDFTs) (1010), to generate a plurality of symbols, e.g.,Sym0, Sym1, . . . , and Sym4 including information regarding the first10 bits. The target UE may additionally generate symbols includingdemodulation reference signals (DM-RS) by applying CS codes CS1 and CS5(1012) and IDFTs (1012) to a ZC base sequence. Accordingly, the targetUE may transmit the discovery signal, including the symbolscorresponding to the first 10 bits and the reference symbols DM-RS, in afirst time slot on the PUCCH. Similarly, the target UE may transmit thediscovery signal, including symbols corresponding to the last 10 bitsand the reference symbols DM-RS, in a second time slot on the PUCCH. Insome approaches, the target UE may transmit a discovery signal using asubset of the elements in FIG. 10, e.g., based on the number of symbolsincluded in a resource block.

In one example approach, the first and second time slots may be used fordifferent UEs. In another example approach, locations of referencesignals whose transmit power is different than that of the temporary D2DUE ID information may be permuted into other symbols within a time slotto multiplex additional UEs. In this case, the base station may transmitcontrol information including a bitmap of reference signals on the PDCCHor on the PDSCH via the PDCCH.

FIG. 11 is a diagram illustrating a method 1100 for a target UE totransmit a discovery signal on the PUCCH, according to an exampleapproach. Referring to FIG. 11, the target UE may use a channel encoderto encode its assigned temporary D2D UE ID, which has a length of, e.g.,10 bits, with a convolutional code, such as a rate (16, k) convolutionalcode, to generate 16 coded bits (1102), where k is the bit length of thetemporary D2D UE ID. The target UE may then modulate the first 8 bits ofthe 16 bits with the QPSK modulation (1104) followed by aserial-to-parallel (SIP) conversion (1106). For the output of the S/Pconversion, the target UE may further apply each CS code CS0, CS1, CS5,and CS6 (1108), and apply inverse discrete Fourier transforms (IDFTs)(1110), to generate a plurality of symbols, e.g., Sym0, Sym1, Sym2, andSym3, including information regarding the first 8 bits. The target UEmay additionally generate symbols including demodulation referencesignals (DM-RS) by applying CS codes CS2, CS3, and CS4 (1114) and IDFTs(1116) to a ZC base sequence. Accordingly, the target UE may transmitthe discovery signal, including the symbols corresponding to the first 8bits and the reference symbols DM-RS, in a first time slot on the PUCCH.Similarly, the target UE may transmit the discovery signal, includingsymbols corresponding to the last 8 bits and the reference symbolsDM-RS, in a second time slot on the PUCCH. In some approaches, thetarget UE may transmit a discovery signal using a subset of the elementsin FIG. 11, e.g., based on the number of symbols included in a resourceblock.

In example approaches, a pseudo semi-static approach may be used formultiple UEs to transmit their respective discovery signals, to reduceoverhead due to dynamic allocation and to efficiently utilize resourceblocks. In one example approach, based on the pseudo semi-staticapproach, a periodicity, a transmission duration, and a time offset totransmit discovery signals from a current subframe may be transmitted tothe UEs on the PDCCH or on the PDSCH. Furthermore, additionalinformation may be transmitted on the PDCCH or on the PDSCH to stopperiodic discovery signal transmission from the UEs. In one exampleapproach, when multiple UEs are scheduled via the PDSCH, the UEs aredivided into a plurality of groups based on the multiplexing capabilityof the assigned PUSCH, and the discovery signals from each group aretransmitted on the assigned PUSCH.

The devices and methods described above may be implemented by anyhardware, software or a combination of hardware and software having theabove described functions. The software code, either in its entirety ora part thereof, may be stored in a computer readable memory, which maybe a tangible, non-transitory computer readable memory.

While several implementations have been provided in the presentdisclosure, it should be understood that the disclosed devices andmethods may be implemented in many other specific forms withoutdeparting from the scope of the present disclosure. The present examplesare to be considered as illustrative and not restrictive, and theintention is not to be limited to the details given herein. For example,the various elements or components may be combined or integrated inanother system or certain features may be omitted, or not implemented.Method steps may be implemented in an order that differs from thatpresented herein.

Also, techniques, systems, subsystems, and methods described andillustrated in the various implementations as discrete or separate maybe combined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

While the above detailed description has shown, described, and pointedout the fundamental novel features of the disclosure as applied tovarious implementations, it will be understood that various omissionsand substitutions and changes in the form and details of the systemillustrated may be made by those skilled in the art, without departingfrom the intent of the disclosure. Although certain illustrated examplesin this disclosure may show only two UEs, the described systems andmethods for the inter-device communications can be applied to more thantwo UEs without departing from the scope of the present disclosure.

What is claimed is:
 1. A method for use in a first user equipment (UE),comprising: receiving, from a base station, control information and aresource assignment for uplink transmission; and transmitting, based onthe control information, a discovery signal on the assigned resource foruplink transmission, the discovery signal including a first temporary UEidentifier (ID) assigned to the first UE, wherein the first temporary UEID is used to identify the first UE for device-to-device communication.2. The method of claim 1, further comprising: receiving, from the basestation, a second temporary UE ID assigned to a second UE; andperforming device-to-device communication with the second UE.
 3. Themethod of claim 1, before receiving the control information and theresource assignment, further comprising: transmitting, to the basestation, an indication message indicating the first UE's capability ofperforming proximity discovery; and receiving, from the base station,the first temporary UE ID.
 4. The method of claim 1, wherein receivingthe control information and the resource assignment comprises:receiving, on a physical downlink control channel (PDCCH), the controlinformation and the resource assignment for uplink transmission.
 5. Themethod of claim 1, wherein receiving the control information and theresource assignment comprises: receiving, on a physical downlink controlchannel (PDCCH), a resource assignment for a physical downlink sharedchannel (PDSCH); and receiving, on the PDSCH, the control informationand the resource assignment for uplink transmission.
 6. The method ofclaim 1, wherein transmitting the discovery signal comprises:transmitting the discovery signal on a physical uplink shared channel(PUSCH), based on the resource assignment for uplink transmission. 7.The method of claim 6, further comprising: encoding the first temporaryUE ID with one of a tail-biting convolutional code or a turbo code togenerate the discovery signal.
 8. The method of claim 1, whereintransmitting the discovery signal comprises: transmitting the discoverysignal on a physical uplink control channel (PUCCH), based on theresource assignment for uplink transmission.
 9. The method of claim 8,further comprising: encoding the first temporary UE ID with one of aconvolutional code or a Reed-Muller code to generate the discoverysignal.
 10. The method of claim 2, further comprising: receiving, fromthe base station, an announcement message notifying the first UE of aresource assignment for the second UE for uplink transmission; detectingthe second temporary UE ID on the assigned resource for the second UEfor uplink transmission; and transmitting, to the base station, areporting message reporting the second temporary UE ID being detected.11. User equipment (UE) for performing device-to-device communication,comprising: a processor; and a memory for storing instructionsexecutable by the processor, wherein the processor is configured to:receive, from a base station, control information and a resourceassignment for uplink transmission; transmit, based on the controlinformation, the discovery signal on the assigned resource for uplinktransmission, the discovery signal including a temporary UE identifier(ID) assigned to the UE, wherein the temporary UE identifier ID is usedto identify the UE for device-to-device communication.
 12. A method foruse in a base station, comprising: assigning a first temporary userequipment (UE) identifier (ID) and a second temporary UE ID to a firstUE and a second UE, respectively; transmitting, to the first UE, controlinformation and a resource assignment for uplink transmission;transmitting, to the second UE, an announcement message to notify thesecond UE of the resource assignment; receiving, from the second UE, areporting message reporting the first temporary UE ID being detected;and transmitting, to the first UE, the second temporary UE ID assignedto the second UE.
 13. The method of claim 12, wherein assigning thefirst temporary UE ID and the second temporary UE ID comprises:receiving a first indication message from the first UE, the firstindication message indicating the first UE's capability of performingdevice-to-device communication; assigning, in response to receiving thefirst indication message, the first temporary UE ID to the first UE;receiving a second indication message from the second UE, the secondindication message indicating the second UE's capability of performingdevice-to-device communication; and assigning, in response to receivingthe second indication message, the second temporary UE ID to the secondUE.
 14. The method of claim 12, further comprising: receiving, from thefirst UE, a request for performing proximity discovery; andtransmitting, in response to receiving the request, the controlinformation the resource assignment for uplink transmission.
 15. Themethod of claim 12, further comprising: transmitting, on a physicaldownlink control channel (PDCCH), the control information and theresource assignment for uplink transmission.
 16. The method of claim 15,wherein transmitting on the PDCCH the resource assignment comprises:generating a cyclic redundancy check (CRC) code for a message includingthe resource assignment for uplink transmission; scrambling thegenerated CRC code with a radio network temporary identifier (RNTI)assigned to the first UE; and transmitting, on the PDCCH, the messagewith the scrambled CRC code appended thereto.
 17. The method of claim12, further comprising: transmitting, on a physical downlink controlchannel (PDCCH), a resource assignment for a physical downlink sharedchannel (PDSCH); and transmitting, on the PDSCH, the control informationand the resource assignment for uplink transmission.
 18. The method ofclaim 12, wherein transmitting the control information comprises:transmitting a modulation and coding scheme for a discovery signal to betransmitted by the first UE.
 19. The method of claim 12, whereintransmitting the control information comprises: transmitting a signalpattern for a discovery signal to be transmitted by the first UE. 20.The method of claim 12, wherein transmitting to the first UE the secondtemporary UE ID comprises: authenticating a relationship between thefirst UE and the second UE; and upon authentication, transmitting to thefirst UE the second temporary UE ID assigned to the second UE.
 21. Abase station in a wireless network, comprising: a processor; and amemory storing instructions executable by the processor, wherein theprocessor is configured to: assign a first temporary user equipment (UE)identifier (ID) and a second temporary UE ID to a first UE and a secondUE, respectively; transmit, to the first UE, control information and aresource assignment for uplink transmission; transmit, to the second UE,an announcement message to notify the second UE of the resourceassignment; receive, from the second UE, a reporting message reportingthe first temporary UE ID being detected; and transmit, to the first UE,the second temporary UE ID assigned to the second UE.
 22. Anon-transitory computer-readable medium including instructions,executable by a processor, to cause a first user equipment (UE) toperform a method, the method comprising: receiving, from a base station,control information and a resource assignment for uplink transmission;and transmitting, based on the control information, a discovery signalon the assigned resource for uplink transmission, the discovery signalincluding a first temporary UE identifier (ID) assigned to the first UE,wherein the first temporary UE ID is used to identify the first UE fordevice-to-device communication.
 23. A non-transitory computer-readablemedium including instructions, executable by a processor, to cause abase station to perform a method, the method comprising: assigning afirst temporary user equipment (UE) identifier (ID) and a secondtemporary UE ID to a first UE and a second UE, respectively;transmitting, to the first UE, control information and a resourceassignment for uplink transmission; transmitting, to the second UE, anannouncement message to notify the second UE of the resource assignment;receiving, from the second UE, a reporting message reporting the firsttemporary UE ID being detected; and transmitting, to the first UE, thesecond temporary UE ID assigned to the second UE.